1. Field of the Invention
The present invention relates to a two-component developing agent in an image-forming apparatus such as a digital copying machine and a printer.
2. Description of the Related Art
In copying machines or printers of the electrophotographic system, a two-component developing agent composed of a toner and a carrier has been commonly used for developing an electrostatic latent image formed on an image-supporting member such as a photosensitive member. The two-component developing agent is used in a two-component developing system. In this system, the toner is frictionally charged by the carrier while the developing agent is being stirred, and the charged toner is used in a developing process.
With respect to carriers used for the two-component developing agent, various carriers, such as iron power carrier, ferrite carrier, resin-coated carrier in which these magnetic particles are coated with resin, and binder carrier in which magnetic fine particles are dispersed in binder resin, have been known.
However, the problem with the conventional two-component developing agent is that as the developing agent is used for a long time, fog tends to occur in copied images, the image density tends to decrease, and unevenness (density unevenness) tend to occur in images.